//Courtesy of Sameera Perera -- check http://www.codoxide.com/post/My-Favorite-Database-Wrapper-for-C.aspx
using System;
using System.Collections.Generic;
using System.Text;
using System.Data;
using System.Data.Common;

namespace nsDb
{
    //comm -- / <summary>
    //comm -- / Abstract base class for encapsulating provider independant database interactin logic. 
    //comm -- / </summary>
    //comm -- / <typeparam name="CONNECTION_TYPE"><see cref="DbConnection"/> derived Connection type.</typeparam>
    //comm -- / <typeparam name="COMMAND_TYPE"><see cref="DbCommand"/> derived Command type.</typeparam>
    //comm -- / <typeparam name="ADAPTER_TYPE"><see cref="DbDataAdapater"/> derived Data Adapter type.</typeparam>
    public abstract 
        class AbstractDatabase<CONNECTION_TYPE, COMMAND_TYPE, ADAPTER_TYPE> : IDisposable
        where CONNECTION_TYPE : DbConnection, new()
        where COMMAND_TYPE : DbCommand
        where ADAPTER_TYPE : DbDataAdapter, new()
    {
        #region : Connection :

        //comm -- / <summary>Gets the Connection object associated with the current instance.</summary>
        public DbConnection Connection
        {
            get
            {
                if (internal_currentConnection == null)
                {
                    internal_currentConnection = new CONNECTION_TYPE();
										//debugOk - Enable to measure the connection time Utils.Debugger.WriteIf ( "GetConnectionString START" );
                    internal_currentConnection.ConnectionString = GetConnectionString();
										//debugOk - Enable to measure the connection time Utils.Debugger.WriteIf ( "GetConnectionString END" );
                }
                return internal_currentConnection;
            }
        }
        private DbConnection internal_currentConnection;

        //comm -- / <summary>When overridden in derived classes returns the connection string for the database.</summary>
        //comm -- / <returns>The connection string for the database.</returns>
        protected abstract string GetConnectionString();

        #endregion

        #region : Commands :

        //comm -- / <summary>Gets a DbCommand object with the specified <see cref="DbCommand.CommandText"/>.</summary>
        //comm -- / <param name="sqlString">The SQL string.</param>
        //comm -- / <returns>A DbCommand object with the specified <see cref="DbCommand.CommandText"/>.</returns>
        public DbCommand GetSqlStringCommand(string sqlString)
        {
            if (this.Connection.State != ConnectionState.Open)
                this.Connection.Open();

            DbCommand cmd  = this.Connection.CreateCommand();
            cmd.CommandType = CommandType.Text;
            cmd.CommandText = sqlString;
            return cmd;
        }

        //comm -- / <summary>Gets a DbCommand object with the specified <see cref="DbCommand.CommandText"/>.</summary>
        //comm -- / <param name="sqlStringFormat">The SQL string format.</param>
        //comm -- / <param name="args">The format arguments.</param>
        //comm -- / <returns>A DbCommand object with the specified <see cref="DbCommand.CommandText"/>.</returns>
        public DbCommand GetSqlStringCommand(string sqlStringFormat, params object[] args)
        {
            return GetSqlStringCommand(string.Format(sqlStringFormat, args));
        }

        //comm -- / <summary>Gets a DbCommand object for the specified Stored Procedure.</summary>
        //comm -- / <param name="storedProcName">The name of the stored procedure.</param>
        //comm -- / <returns>A DbCommand object for the specified Stored Procedure.</returns>
        public DbCommand GetStoredProcedureCommand(string storedProcName)
        {
            if (this.Connection.State != ConnectionState.Open)
                this.Connection.Open();

            DbCommand cmd    = this.Connection.CreateCommand();
            cmd.CommandType   = CommandType.StoredProcedure;
            cmd.CommandText   = storedProcName;
            return cmd;
        }

        #region : Parameters :

        //comm -- / <summary>Adds an input parameter to the given <see cref="DbCommand"/>.</summary>
        //comm -- / <param name="cmd">The command object the parameter should be added to.</param>
        //comm -- / <param name="paramName">The identifier of the parameter.</param>
        //comm -- / <param name="paramType">The type of the parameter.</param>
        //comm -- / <param name="value">The value of the parameter.</param>
        //comm -- / <returns>The <see cref="DbParameter"/> that was created.</returns>
        public DbParameter AddInParam(DbCommand cmd, string paramName, DbType paramType, object value)
        {
            DbParameter param       = cmd.CreateParameter();
            param.DbType            = paramType;
            param.ParameterName     = paramName;
            param.Value             = value;
            param.Direction         = ParameterDirection.Input;
            cmd.Parameters.Add( param );
            return param;
				} //eof method AddInParam

        //comm -- / <summary>Adds an input parameter to the given <see cref="DbCommand"/>.</summary>
        //comm -- / <param name="cmd">The command object the parameter should be added to.</param>
        //comm -- / <param name="paramName">The identifier of the parameter.</param>
        //comm -- / <param name="paramType">The type of the parameter.</param>
        //comm -- / <param name="size">The maximum size in bytes, of the data table column to be affected.</param>
        //comm -- / <param name="value">The value of the parameter.</param>
        //comm -- / <returns>The <see cref="DbParameter"/> that was created.</returns>
        public DbParameter AddInParam(DbCommand cmd, string paramName, DbType paramType, int size, object value)
        {
            DbParameter param       = cmd.CreateParameter();
            param.DbType            = paramType;
            param.ParameterName     = paramName;
            param.Size              = size;
            param.Value             = value;
            param.Direction         = ParameterDirection.Input;
            //debug Utils.Debugger.WriteIf ( "Adding IN param " + value.ToString ( ) );
            cmd.Parameters.Add(param);
            return param;
        }

        public DbParameter AddInOutParam ( DbCommand cmd, string paramName, DbType paramType, int size, object value )
            {
            DbParameter param = cmd.CreateParameter ( );
            param.DbType = paramType;
            param.ParameterName = paramName;
            param.Size = size;
            param.Value = value;
            param.Direction = ParameterDirection.Output;
            cmd.Parameters.Add ( param );
            //debugOk Utils.Debugger.WriteIf ( "Adding INOUT " + value.ToString ( ) );
            return param;
            }


        public DbParameter AddInOutParam ( DbCommand cmd, string paramName, DbType paramType, object value )
            {
            DbParameter param = cmd.CreateParameter ( );
            param.DbType = paramType;
            param.ParameterName = paramName;
            param.Value = value;
            param.Direction = ParameterDirection.Output;
            cmd.Parameters.Add ( param );
            return param;
            }

        #endregion

        #region : Executes :

        //comm -- / <summary>Executes the specified command against the current connection.</summary>
        //comm -- / <param name="cmd">The command to be executed.</param>
        //comm -- / <returns>Result returned by the database engine.</returns>
        public int ExecuteNonQuery(DbCommand cmd)
        {
            if (this.Connection.State != ConnectionState.Open)
                this.Connection.Open();

            return cmd.ExecuteNonQuery();
        }

        //comm -- / <summary>Executes the specified command against the current connection.</summary>
        //comm -- / <param name="cmd">The command to be executed.</param>
        //comm -- / <param name="txn">The database transaction inside which the command should be executed.</param>
        //comm -- / <returns>Result returned by the database engine.</returns>
        public int ExecuteNonQuery(DbCommand cmd, DbTransaction txn)
        {
            if (this.Connection.State != ConnectionState.Open)
                this.Connection.Open();

            cmd.Transaction = txn;
            return cmd.ExecuteNonQuery();
        }

        //comm -- / <summary>Executes the specified command against the current connection.</summary>
        //comm -- / <param name="cmd">The command to be executed.</param>
        //comm -- / <returns>Result returned by the database engine.</returns>
        public DbDataReader ExecuteReader(DbCommand cmd)
        {
            if (this.Connection.State != ConnectionState.Open)
                this.Connection.Open();

            return cmd.ExecuteReader();
        }

        //comm -- / <summary>Executes the specified command against the current connection.</summary>
        //comm -- / <param name="cmd">The command to be executed.</param>
        //comm -- / <param name="behavior">One of the <see cref="System.Data.CommandBehavior"/> values.</param>
        //comm -- / <returns>Result returned by the database engine.</returns>
        public DbDataReader ExecuteReader(DbCommand cmd ,  CommandBehavior behavior )
        {
            if (this.Connection.State != ConnectionState.Open)
                this.Connection.Open();

            return cmd.ExecuteReader(behavior);
        }

        //comm -- / <summary>Executes the specified command against the current connection.</summary>
        //comm -- / <param name="cmd">The command to be executed.</param>
        //comm -- / <returns>Result returned by the database engine.</returns>
        public T ExecuteScalar<T>(DbCommand cmd, T defaultValue)
        {
            if (this.Connection.State != ConnectionState.Open)
                this.Connection.Open();

            object retVal = cmd.ExecuteScalar();
            if (null == retVal || DBNull.Value == retVal)
                return defaultValue;
            else
                return (T)retVal;
        }

        //comm -- / <summary>Executes the specified command against the current connection.</summary>
        //comm -- / <param name="cmd">The command to be executed.</param>
        //comm -- / <returns>Result returned by the database engine.</returns>
        public DataSet ExecuteDataSet(DbCommand cmd)
        {
            ADAPTER_TYPE adapter  = new ADAPTER_TYPE();
            adapter.SelectCommand = (COMMAND_TYPE)cmd;

            DataSet retVal = new DataSet();
            adapter.Fill(retVal);
            return retVal;
        }

        #endregion

        #endregion

        //comm -- / <summary>Begins a transaction.</summary>
        //comm -- / <returns>Created transaction.</returns>
        public DbTransaction BeginTransaction()
        {
            if (this.Connection.State != ConnectionState.Open)
                this.Connection.Open();
            return Connection.BeginTransaction();
        }

        #region : Construction / Destruction :

        //comm -- / <summary>Disposes the resources associated with the current database connection.</summary>
        ~AbstractDatabase()
        {
            Dispose();
        }

        #region IDisposable Members

        //comm -- / <summary>Disposes the resources associated with the current database connection.</summary>
        public void Dispose()
        {
            if (null != internal_currentConnection)
            {
                internal_currentConnection.Dispose();
                internal_currentConnection = null;
            }
        }

        #endregion

        #endregion

    } //eof public abstract class AbstractDatabase
} //eof namespace nsDb 
